The present invention relates generally to lithographic exposure equipment, and more particularly, to a photolithography system and method, such as can be used in the manufacture of semiconductor integrated circuit devices.
In conventional photolithography systems, the photographic equipment requires a mask for printing a pattern onto a subject. The subject may include, for example, a photo resist coated semiconductor substrate for manufacture of integrated circuits, metal substrate for etched lead frame manufacture, conductive plate for printed circuit board manufacture, or the like. A patterned mask or photomask may include, for example, a plurality of lines, structures, or images. During a photolithographic exposure, the subject must be aligned to the mask very accurately using some form of mechanical control and sophisticated alignment mechanism.
U.S. Pat. No. 5,691,541, which is hereby incorporated by reference, describes a maskless, reticle-free lithography system. The system employs a pulsed or strobed eximer laser to reflect light off a programmable digital mirror device (DMD) for projecting a line image onto a substrate. The substrate is mounted on a stage that is projected during the sequence of pulses.
U.S. Pat. No. 4,925,279, which is hereby incorporated by reference, describes a telecentric F-xcex8 lens system that employs a coherent light source (laser) to direct a beam of light through an F-xcex8 lens system and onto a subject. The beam of light scans a line across the subject to produce a resulting image.
The above-two described systems suffer from a very small exposure area with relatively poor resolution. Being line scanning systems, each system requires a relatively large amount of time for the entire surface of the substrate to be exposed. In addition, the coherent light sources (used for lasers) are not only very expensive, but are unreliable. Further still, F-xcex8 lenses are extremely expensive.
U.S. Pat. Ser./No. 09/480,796, filed Jan. 10, 2000 and hereby incorporated by reference, discloses a novel system and method for photolithography which projects a moving pixel image onto specific sites of a subject. A xe2x80x9csitexe2x80x9d may represent a single pixel, or a group of pixels, depending on the embodiment. In one embodiment, the method projects a pixel-mask pattern onto a subject such as a wafer. The method provides a sub-pattern to a pixel panel pattern generator such as a deformable mirror device or a liquid crystal display. The pixel panel provides a plurality of pixel elements corresponding to the sub-pattern that may be projected onto the subject.
Each of the plurality of pixel elements is then simultaneously focused to discrete, non-contiguous portions of the subject. The subject and pixel elements are then moved and the sub-pattern is changed responsive to the movement and responsive to the pixel-mask pattern. As a result, light can be projected into the sub-pattern to create the plurality of pixel elements on the subject, and the pixel elements can be moved and altered, according to the pixel-mask pattern, to create a contiguous image on the subject.
Certain improvements are desired for maskless photolithograph systems in general, such as the above-described systems and methods. For example, it is desirable to have a relatively large exposure area, to provide good image resolution, to provide good redundancy, to use a relatively inexpensive incoherent light source, to provide high light energy efficiency, to provide high productivity and resolution, and to be more flexible and reliable.
A technical advance is provided by a novel method and system for performing digital lithography onto a subject. In one embodiment, the system comprises first and second panels for generating first and second patterns, each pattern comprising a plurality of pixel elements, a first mirror for diverting the pixel elements of the first pattern to align with the pixel elements of the second pattern, a first gradient lens system positioned between the first and second panels and the subject for simultaneously directing the pixel elements to the subject, and means for providing relative movement between the first and second panels and the subject to scan the pixel elements across the subject.
In another embodiment, the system comprises third and fourth panels for generating third and fourth patterns, a second mirror for diverting the pixel elements of the third pattern to align with the pixel elements of the fourth pattern, and a second gradient lens system positioned between the third and fourth panels and the subject for simultaneously directing the pixel elements to the subject. The system is operable to scan the pixel elements from the first and second panels across a first surface of the subject, and to scan the pixel elements from the third and fourth panels across a second surface of the subject. In yet another embodiment, the first and second surfaces are on opposite sides of the subject.
In still another embodiment, the system comprises a point array unit and means for providing relative movement between the unit and a subject to scan the pixel elements across the subject. The point array unit includes a panel for generating the pattern, a first lens system positioned between the panel and the subject for directing the pixel elements to the subject, and a second lens system for focusing the pixel elements.